1. Field of the Invention
The present invention generally relates to a coating machine, and more particularly, to a coater gap control arrangement provided in the coating machine.
2. Description of the Prior Art
A coating machine, hereinafter referred to as a coater, is generally used for coating the surface of a workpiece with coating material such as paint or the like. In the coater, the workpiece is transported by a back-up roll rotatably mounted in the machine. There have been proposed various methods for controlling the gap between the back-up roll and a coater head for supplying the coating material to the surface of the workpiece.
When the workpiece is a web such as a long film, paper or the like, its thickness finely changes in general, resulting in the change of a film of coating.
Conventionally, an operator is required to move the coater head while observing the thickness of the film of coating at all times so that the film of coating may be uniformly formed on the workpiece. Alternatively, the operator is required to measure the thickness of the workpiece in any known method and to move the coater head on the basis of the measured data.
In the former, however, it is very difficult to detect the change of the thickness of the film of coating caused by the fine change of the thickness of the workpiece.
On the other hand, in the latter, it is extremely troublesome to move the coater head in association with the change of the thickness of the workpiece.